150627-50-2Relevant academic research and scientific papers
Synthesis, dynamic behavior, and catalytic activity of the ether-phosphine complex Rh(P O)(P～O)Cl and its reactivity toward hydrogen, oxygen, methyl iodide, and acetyl chloride
Lindner, Ekkehard,Wang, Qinyan,Mayer, Hermann August,Bader, Armin,Kühbauch, Hartwig,Wegner, Peter
, p. 3291 - 3296 (2008/10/08)
The complex ClRh(P～O)(P O) (1; P O = η2(O,P)-chelated Cy2PCH2CH2OCH3 ligand; P～O = η1(P) coordinated) exhibits fluxional behavior on the 31P NMR time scale. Line-shape analysis of variable-temperature 31P{1H} NMR spectra of 1 yields values of ΔH? = 43.0 ± 3.4 kJ mol-1 and ΔS? = -42 ± 11.8 J mol-1 K-1, indicating an associative mechanism of the dynamic process involving a five-coordinate species. Hydrogenation of 1-hexene to n-hexane over complex 1 as precatalyst proceeds with 100% selectivity and excellent activity (turnover number 7920 h-1) under mild conditions (300 K, 40 bar of H2). Oxidative addition of H2 and O2 results in the formation of the unstable dihydridorhodium(III) complex ClRhH2(P～O)2 (2) and the relatively stable (dioxygen)rhodium(III) complex ClRhO2(P～O)(P O) (3), respectively. The reaction of methyl iodide and acetyl chloride with complex 1 affords the products of the oxidative addition in trans fashion (CH3(Cl)(I)Rh(P～O)(P O) (5a), CH3C(O)Cl2Rh(P～O) (P O) (6a)) and cis fashion (CH3(Cl)(I)Rh(P～O)2 (5b), CH3(I)(Cl)Rh(P～O)2 (5c), CH3C(O)Cl2Rh(P～O)2 (6b)). The use of labeled 13CH3I and CH313C(O)Cl supports the structural characterization of all isomers by 31P{1H} and 13C{1H} NMR spectroscopy. When it is warmed in CDCl3, 5a′ is irreversibly converted into 5b′ and 5c′ (5a′, 5b′, and 5c′ = 13CH3-labeled isomers of complex 5). First-order kinetics in 5a′ with'a rate constant of 7.67 × 10-5 s-1 at 287 K is established. The carbonylation of 5b (5b′) gives a mixture of IRhCO(P～O)2 (8) and CH3C(O)Rh(I)(Cl)(P～O)2 (9; 9′ = CH313C-(O)-labeled analogue of 9) via the unstable intermediate 7. The progress of the reaction is monitored, and the compounds 8,9 (9′), and 13CH3Cl are identified by 31P{1H} and 13C{1H} NMR spectroscopy.
